The invention relates to the manufacture of fluid ejection devices, more specifically, the invention relates to fluid ejection devices used in fluid ejection cartridges and fluid delivery devices such as printers.
One type of fluid-jet printing system uses a piezoelectric transducer to produce a pressure pulse that expels a droplet of fluid from a nozzle. A second type of fluid-jet printing system uses thermal energy to produce a vapor bubble in a fluid-filled chamber that expels a droplet of fluid. The second type is referred to as thermal fluid-jet or bubble jet printing systems.
Conventional thermal fluid-jet printers include a print cartridge in which small droplets of fluid are formed and ejected towards a printing medium. Such print cartridges include fluid-jet printheads with orifice structures having very small nozzles through which the fluid droplets are ejected. Adjacent to the nozzles inside the fluid-jet printhead are fluid chambers, where fluid is stored prior to ejection. Fluid is delivered to fluid chambers through fluid channels that are in fluid communication with a fluid supply. The fluid supply may be, for example, contained in a reservoir part of the print cartridge.
Ejection of a fluid droplet, such as ink, through an orifice opening (nozzle) may be accomplished by transferring energy to a volume of fluid within the adjacent fluid chamber, such as with heat or mechanical energy. For example, the transfer of heat causes a rapid expansion of vapor in the fluid. The rapid expansion of fluid vapor forces a drop of fluid through the nozzle in the orifice structure. This process is commonly known as xe2x80x9cfiring.xe2x80x9d The fluid in the chamber may be heated with a transducer, such as a resistor, that is disposed and aligned adjacent to the nozzle.
The printhead substructure is overlaid with at least one orifice layer. Preferably, the at least one orifice layer is etched to define the shape of the desired firing fluid chamber within the at least one orifice layer. The fluid chamber is situated above, and aligned with, the resistor. The at least one orifice layer is preferably formed with a polymer coating or optionally made of an fluid barrier layer and an orifice plate. Other methods of forming the orifice layer(s) are know to those skilled in the art.
In direct drive thermal fluid-jet printer designs, the thin-film device is selectively driven by electronics preferably integrated within the integrated circuit part of the printhead substructure. The integrated circuit conducts electrical signals directly from the printer microprocessor to the resistor through conductive layers. The resistor increases in temperature and creates super-heated fluid bubbles for ejection of the fluid from the fluid chamber through the nozzle. To prevent the resistor from overheating and causing premature ejection of fluid from the fluid chamber, the fluidic structure must be designed to both transfer heat efficiently to the fluid in the fluid chamber during firing and after firing, to transfer excess residual heat into the printhead and fluid not in the fluid chamber to allow the resistor to cool sufficiently before firing reoccurs. As the firing frequency increases, the heat transfer characteristic of the fluidic design becomes critical in avoiding thermal build-up to provide consistent bubble nucleation.
It is desirous to fabricate a fluid-jet printhead capable of producing fluid droplets having consistent and reliable drop shapes and weights to maintain print quality.
The invention is a fluid ejection device, such as a printhead, that has a substrate with a first surface mating to an orifice layer, preferably through a stack of thin-film layers. The orifice layer defines a fluid chamber interfacing to an orifice opening or nozzle. The substrate has a second surface having a truncated pyramidal structure; either polyhedral or triangular ridge shaped defining an opening through the substrate to the fluid chamber. The substrate further has an ejection element, preferably disposed as a resistor in the stack of thin-film layers. When energy is transferred from the ejection element to the fluid in the fluid chamber, fluid is ejected from the orifice opening. The fluid ejection device may have one or a plurality of fluid chambers and one or a plurality of frustums of a truncated polyhedral, truncated pyramidal, truncated conical or truncated triangular cross-sectional ridge structures defining openings from the second surface of the substrate to the fluid chambers.